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How might the Dover area have looked 87 million years ago?

Introduction

Dover is a coastal town and major port in the southeast corner of
Kent, and home to over 28,000 people. The town is well known as a
crossing point between England and Calais in France, a journey across
the English Channel of 21 miles. Maritime evidence dating from c.4,000
years ago reveals Dover has long been used by people travelling to and
from
the continent, however it's the fossil evidence that predates human
endeavours by many millions of years that is the subject of particular
interest here.

Immediately east of the town and continuing 2 miles towards St
Margaret's Bay are the famous White Cliffs of Dover, an exposure of
Middle and Upper Chalk dating from the Late Cretaceous epoch, 89-85 million years
ago. At this time the Dover area lay beneath a relatively shallow sea,
over a hundred miles from the nearest land. Fossils reveal the prehistoric
sea was
home to a variety of organisms, in
particular sediment burrowing echinoids, bivalves,
sponges and other marine organisms including crustaceans and sharks.

Access to the cliffs and beach is made from the hill-top, from which
it's a fair walk along the coast to Langdon Hole, where a zigzag path
descends the cliff-face. Parking is available along Upper Road or within
the National Trust pay-and-display car park shown below.

Left: Limited roadside parking is available along
Upper Road.
Right: Alternatively a National Trust pay-and-display car park is available further along the road.

From the car park a number of well trodden routes connect with
several major footpaths travelling broadly east and west along the
cliff-top. The best route is towards the east via the lowest
footpath, which briefly heads towards the west beneath the car
park, before taking a sharp-left and descending to the cliff-edge.

Left: View from the
lower coastal footpath looking back
across Dover Port.
Right: Lucinda overlooks the ferry terminals and
lower footpath from the cliff-top.

The footpath continues along the coast before descending steeply
into Langdon Hole (shown below-left) - a shallow eroded valley
formed by seasonal melt water towards the end of the recent ice age,
14,500 years ago (see the
Seaford Head report for more details of eroded chalk
valleys). Follow the path into Langdon Hole and up the other side.
Shortly before reaching the top of the other side, a narrow path
leads off to the right and zigzags down the cliff-face. At the
bottom of the path a ladder spans the remaining 8 metres to the
beach (shown below-right).

Left: The coastal
path descends steeply into Langdon Hole. Right: Langdon Stairs
zigzag down the cliff-face to a ladder which connects to the beach.

The geology of Dover

Figure 1: Summary of
the geological horizons present in the cliff-face between Dover and
Crab Bay.

The chalk exposed east of Dover belongs predominately to the Upper Chalk, and
was deposited during the Turonian and Coniacian stages of the
Late
Cretaceous epoch between 89-85 million years ago (mya). At this time
the Dover area and much of Great Britain, along with Europe, lay beneath a
relatively shallow sea approximately 40°N of the equator, on an equivalent latitude to the
Mediterranean Sea today.

In comparison with present-day conditions, global sea-levels during
the Late Cretaceous were over 200 metres higher. The higher sea levels
likely reflect a combination of extreme greenhouse conditions and
heightened plate tectonics. Elevated plate tectonic activity and the
associated volcanics delivered greenhouse gases to the atmosphere,
fuelling the greenhouse effect. Global high temperatures melted much
(perhaps all) of the ice at high latitudes, introducing significant
amounts of water to the world's oceans. Uplift of the ocean-floor in
regions of active plate tectonics displaced further water onto the
continental shelves.

The evidence of higher sea levels is reflected in the white chalk
at Dover. The purity of the chalk indicates its formation took place
far from land, mostly free of terrestrial sands and silts that would
otherwise have coloured it. Evidence indicates the nearest landmass
was where Wales is today. At Dover the lower half of the cliff and
foreshore contains a slightly greater volume of land-sourced
sediment, this is particularly evident in the hardgrounds described
below. Chalk is
largely comprised of the skeletal remains of planktonic algae
known as coccolithophores which accumulated to form a white ooze on the
seafloor. This soft sediment was later compacted and hardened
(lithified) to form chalk - a relatively soft rock itself. To
discover more about chalk
click here.

Today the chalk appears above sea level, the
result of lower present-day sea levels and widespread uplifting caused by the pressure of the European
and African continental plates colliding (generating the Alps), a process that took place at
its greatest extent 30-25 mya. More recently, following the end of the
last ice age and subsequent increase in sea levels (albeit to a lesser
extent than 84 mya), the coastline has moved inland,
exposing the elevated chalk to intensive erosion and sculpting it into a
vertical cliff-face.

A short distance east of Langdon Hole a conspicuous layer
of white chalk interspersed with soft, grey chalk, can be seen at
the foot of the cliff and on the foreshore. This layer within the Lewes
Nodular Chalk Formation is known as a hardground complex (shown below).

Hardgrounds are understood to reflect disruptions to the steady
accumulation of chalk forming sediment, during which sedimentation
simply ceased and/or the unconsolidated, soft surface sediments were
stripped away by bottom currents or slumping, exposing the older
consolidated
chalk sediment. Research has shown that a single hardground may have been
exhumed 16 or more times before long-term burial took place. For
more information about hardgrounds see
Seaford Head.

Another striking characteristic of the chalk at Dover is the
presence of
dark-coloured nodular and sheet flints that appear as horizontal
bands in the cliff-face and as loose pebbles on the
beach (shown below).

Left: Horizontal
bands of nodular and sheet flints visible in the cliff-face.
Right: Flint pebbles accumulated on the beach at the foot of the cliff.

Although flint is inorganic, the silica that formed it was
originally sourced from the remains of sea sponges and siliceous
planktonic micro-organisms (diatoms, radiolarians). Flints are
concretions that grew within the sediment after its deposition by
the precipitation of silica; filling burrows/cavities and enveloping
the remains of marine creatures, before dehydrating and hardening
into the microscopic quartz crystals which constitute flint.
Consequently it's common to find fossil evidence of these
creatures
preserved as flint, especially the internal moulds of Micraster
echinoids.

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Where to look for fossils?

Fossils can be found on the foreshore and at the cliff base
in either direction from Langdon Hole, although for the purposes of this
page the focus is towards the northeast (left when looking out to sea). The most productive and safest place
to search for fossils is on the foreshore at low-tide. Chalk boulders
and flint nodules are scattered along the entire stretch, providing a
constant supply of fossils.

Left: A large inoceramid
bivalve visible on the surface on an air-weathered boulder.
Right: Fossils can be found in and among the flint pebbles on the beach.

Please note that any in situ chalk is assigned SSSI
status, which requires visitors avoid damaging (including hammering)
the area. From a fossil collecting perspective this means it's not
permitted to extract specimens that are in situ. Collecting efforts
should be directed towards the loose boulders and pebbles on the
foreshore.

As with all coastal locations, a fossil hunting trip is best
timed to coincide with a falling or low-tide. For a relatively low
one-off cost we recommend the use of Neptune Tides software, which
provides future tidal information around the UK. To download a free
trial
click here. Alternatively a free short range forecast covering
the next 7 days is available on the BBC website
click here.

What fossils might you find?

Below is a selection of fossils discovered at Dover over
several visits. Where possible the genus of each specimen has been indicated, if a confident ID can't be achieved a question mark has
been added to indicate so. Among the more frequent finds include echinoids,
brachiopods, bivalves and sponges; less common finds include
shark teeth and crinoid stems among others.

Left: A
Micraster echinoid, found loose among the beach
pebbles.
Right: A second Micraster, found in
situ within the Lewes Nodular Chalk.

Left: The worn
internal flint mould of a Sternotaxis(?) echinoid,
found loose among the beach pebbles.Right: A tiny internal flint mould of a
Micraster echinoid, found loose among the beach
pebbles.

Left: An Echinocorys
echinoid, found in situ within the Lewes Nodular
Chalk.Right: A Phymosoma(?) echinoid spine, found on the
surface of a fallen boulder.

Left: An Temnocidaris echinoid spine alongside an orange-coloured
sponge, on the
surface of a fallen boulder.Right: A sponge on the surface of a fallen
boulder.

Left: An isolated
fragment of Isocrinus crinoid stem on the air-weathered surface of a
fallen chalk boulder.
Right: A fragment of Enoploclytia(?) lobster claw.

Left: A Lamniform shark
tooth, found within a fallen boulder.
Right: An upturned Gryphaeostrea(?) oyster and
Spondylus(?) valve on
an air-weathered boulder.

Left: A
Concinnithyris brachiopod on the surface of a fallen boulder, probably originating
from the Lewes Nodular Chalk.Right: A large fragment of an inoceramid bivalve
shell.

Left: A flint pebble
containing two inoceramid bivalves. Right: The impression of a Spondylus bivalve
on the surface of a flint pebble, found loose on the beach.

Tools & equipment

It's a good idea to spend some time considering the tools and
equipment you're likely to require while fossil hunting at Dover. Preparation in advance will help ensure your visit is
productive and safe. Below are some of the items you should consider
carrying with you. You can purchase a selection of geological tools
and equipment online from
UKGE.

Left: Walking boots,
a strong bag and sunglasses to protect your eyes from the sun and
dazzling white chalk on sunny days are recommended.Right:
A hammer and chisel are recommended for extracting specimens from
loose boulders.

Hammer:
A strong hammer will be required to split prospective rocks. The
hammer should be as heavy as can be easily managed without causing
strain to the user. For individuals with less physical strength and
children (in particular) we recommend a head weight no more than
500g.

Chisel: A chisel is required in conjunction with a
hammer for removing fossils from the chalk. In most instances a
large chisel should be used for completing the bulk of the work,
while a smaller, more precise chisel should be used for finer work.
A chisel founded from cold steel is recommended as this metal is
especially engineered for hard materials.

Safety glasses: While
hammering rocks there's a risk of injury from rock splinters
unless the necessary eye protection is worn. Safety glasses ensure any splinters are deflected away from the eyes. Eye
protection should also be worn by spectators as splinters can
travel several metres from their origin.

Strong bag: When considering the type of bag to use it's worth setting aside
one that will only be used for fossil hunting, rocks are usually
dusty or muddy and will
make a mess of anything they come in contact with. The bag will also
need to carry a range of accessories which need to
be easily accessible. Among the features recommended include: brightly coloured,
a strong holder construction, back
support, strong straps, plenty of easily accessible pockets and a rain cover.

Walking boots: A good pair of walking boots will
protect you from ankle sprains, provide more grip on
slippery surfaces and keep you dry in wet conditions. During your
fossil hunt you're likely to encounter a variety of terrains so
footwear needs to be designed for a range of conditions.

For more information and examples of tools and equipment
recommended for fossil hunting
click here
or shop online at
UKGE.

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FOSSILS

Protecting your finds

It's important to spend some time considering the best way to
protect your finds onsite, in transit, on display and in storage.
Prior to your visit, consider the equipment and accessories you're
likely to need, as these will differ depending on the type of rock,
terrain and prevailing weather conditions.

When you discover a fossil, examine the surrounding matrix (rock)
and consider how best to remove the specimen without breaking it;
patience and consideration are key. The aim of extraction is to
remove the specimen with some of the matrix attached, as this will
provide added protection during transit and future handling;
sometimes breaks are unavoidable, but with care you should be able
to extract most specimens intact. In the event of breakage,
carefully gather all the pieces together, as in most cases repairs
can be made at a later time.

Safety notice: Fossil hunting can at times pose a risk to personal safety, in particular within environments close to the coast, cliffs
or in quarries and when using the tools and equipment illustrated. Discovering Fossils provides a free resource to inform you about
this fascinating subject and does not accept any liability for decisions made using this information. We recommend all individuals
abide by the fossil hunting guidelines available by clicking on the icon at the top of the page.